In Chapter 9 ("Effort, Discipline, and Letting Go") of Meditation for Dummies author Stephan Bodian discusses an exercise to help break away from clinging in both positive and negative forms:

Holding on tightly and pushing away hard, lusting and hating, defending and attacking — traditionally known as attachment and aversion — are the primary causes of suffering and stress. Along with indifference, they form the proverbial three poisons of meditation lore.

Fortunately, you can cultivate the antidotes to these poisons by practicing the two most important gestures or functions of meditation: accepting and letting go. They're inextricably entwined: Until you accept, you can't let go; until you let go, you have no room to accept again. As one Zen master put it, "Let go of it, and it fills your hand." ...

He goes on to sketch out a 10-20 minute sitting session starting with following the breath and moving on to nonjudgmental awareness of thoughts and feelings, consciously attending to welcoming and then letting go of whatever arises.